Spark Plug (socket) Sizes?

No.

Oh, 40 years ago or so I'll guess...

Nope.

Well, my 1949, 1966, 1969, 1973, and 1993 American vehicles all use

13/16 plugs. In fact, I've never owned a vehicle that used 5/8 plugs. I know that the Chrysler 440 "motorhome" cylinder head required them due to an extra cooling passage near the base of the plug hole, but that's the only application I can think of right off the top of my head.

A long time ago, even before my time, there were spark plugs with a 7/8 hex and 18 mm thread. Now we have 18 mm, 5/8, 13/16 along with 10 mm, 12 mm and

14 mm threads.

| |Is it fair to say that 5/8 and 13/16 were both popularly and widely |used on older American cars? Just as likely to have one or the other |or roughly 50/50? | |My newer Japanese cars all seem to use 13/16. However my newer German |car uses 5/8. | |What is the broadly generalized version of who uses (used) what |when...?

From memory, with all the limitations that brings ...;)

GM came with 5/8" plugs in 1971. Most GM cars use them still Ford can't make up their mind, but 5/8 plugs seem to be the majority today Chrysler - ditto

|I also have a 3/4" spark plug socket that I've never used.

Small engines, as in lawnmower

|I think there is also an 18mm spark plug socket around but donno about |that one either...

Motorcycles

Rex in Fort Worth

Thanks everyone! That really helpded clarify the evolution of all these spark plug sockets I have here!

thanks again